Luminaire



May 5, 1964 K. E. FAIRBAN KS 5 Sheets-Sheet l s cu INVENTO Y ZM @galrro/e/VEY May 5, 1964 K. E. FAIRBANKS 3,131,874

' LUMINAIRE Filed Feb. 27, 1962 5 Sheets-Sheet 2 May 5, 1964 K. E.FAIRBANKS LUMINAIRE 5 Shee'cs-Sheei'l 3 Filed Feb. 27, 1962 LUI a /N VENTo R /fE/v/vfh' Firman/wfg United States Patent O Glass Works, Corning,N.Y., a corporation of New York Filed Feb. 27, 1962, Ser. No. 175,965 6Claims. (Cl. 240-106) This invention relates to luminaires and moreparticularly to luminaires and refractors for use therein which arecapable of directing substantially all light emitted therefromthroughout 180 in horizontal directions about the luminaire and with itsgreatest intensity in directions horizontally separated by approximately148 and at angles of about 72 above nadir.

Such light distribution is especially desirable in luminaires intendedto be mounted on a wall and to distribute light throughout an area infront of the luminaire and along the ground adjacent to the wall in bothdirections from the luminaire, and it is an object of the invention toprovide such a luminaire.

This object is accomplished by the provision of a luminaire having aconcavo-convex refractor in the general form of a frustum of atriangular pyramid but having slightly curved faces, one face of thefrustum having on its exterior surface a series of internally reflectingsurface prisms and the other faces having on each surface thereof seriesof parallel generally triangular refracting surface pr1sms.

The construction of the luminaire is illustrated in the accompanyingdrawing, in which:

FIGURE 1 is a plan View of the interior surface of the refractor,

FIGURE 2 is a side elevational view of the refractor,

FIGURE 3 is a sectional view taken on line 3 3 of FIGURE l,

p FIGURE 4 is a fragmentary plan view of the exterior surface of thebottom of the refractor,

FIGURE 5 is a sectional view taken on line 5 5 of FIGURE 1,

FIGURE 6 is a sectional View taken on line 6 6 of FIGURE 1,

FIGURE 7 is a sectional View taken on line 7 7 of FIGURE 4,

FIGURE 8 is a sectional view taken on line 8 8 of FIGURE 1,

FIGURE 9 is a sectional View taken on line 9 9 of FIGURE 8,

FIGURE 10 is a sectional view taken on line 10-10 of FIGURE 1,

FIGURE l1 is a sectional view taken on line'11 11 of FIGURE 10,

FIGURE 12 is of FIGURE l,

FIGURE 13 is a sectional view taken on line 12-12 a sectional view takenon line 13 13 FIGURE 18 is a polar diagram showing the lateraldistribution of light from the luminaire,

FIGURE 19 is a polar diagram showing the vertical distribution of lightfrom the luminaire, and

FIGURE 20 is a longitudinal sectional view of a luminaire according tothe invention.

The refractor 26 of the present invention is symmetric about a planethrough its longitudinal axis and perpen- "ice dicular to the plane ofits rim 25 (a plane through line 3 3 of FIGURE 1 and perpendicular tothe plane of the paper) and, accordingly the side areas of the refractorwill be described with reference to one of the symmetric parts.

As can be seen from the drawing, the refractor of the inventioncomprises a concavo-convex structure 26 in the general form of atruncated triangular pyramid. The refractor is divided into areas eachhaving an interior surface and an exterior surface, each of which isprovided with several series of parallel refracting or reflectingprisms. Side areas 27 and 28 and base area 29, illustrated in FIGURE 1,contain refracting prisms on both their interior surfaces and theirexterior surfaces, while end area 30, which is intended to be placedfacing the well upon which the luminaire is mounted, has a smoothinterior surface 50 and an exterior surface having thereon a series ofprisms 51, illustrated in FIGURE 5, having the ability by means ofinternal reilection to redirect in the direction of a vertical linethrough the light center substantially all light from the lightcenterfalling directly on surface 50. The configuration of such totallyreccting prisms is well known in the art and, for that reason, will notbe further discussed.

Side areas 27 and 28 of the refractor will be described with referenceto area 27, it being understood that area 28 is symmetric therewith andfunctions similarly.

It is a function of the side areas to direct most of the light from theluminaire along the ground adjacent to the wall upon which the luminaireis mounted. Since it is an object of the invention to spread light onthe ground along the length of the wal-l, for example, along a sidewalknear the wall, the luminaire is designed to emit the greatest amount oflight at horizontal angles approximate- 1y 16 from the wall surface andat vertical angles approximately 72 above nadir.

This light distribution is illustrated in FIGURES 18 and 19. FIGURE 18gives the lateral distribution of candle power values for light emittedfrom the luminaire in a cone having its apex at the light center andhaving its surface 72 about nadir, that is the light rays form angles of18 with the horizontal. The luminaire is mounted with its longitudinalaxis along the 0 line on the diagram, and the candle power curve is seento form a pattern which is substantially symmetric about this line andwhich gives maximum candle power ratings at angles of approximately 74on each side thereof. FIGURE 19 gives the vertical candle power Valuesfor the same luminaire for 74 lateral, that is, the candle powerdistribution through from nadir to zenith in each of two vertical planesthrough the maximum candle power vectors of FIGURE 18 and comprises thesubstantially symmetric lobes on each side of the 0-l80 line.

In order to effect such distribution the side and the bottom areas areconstructed as follows:

Side area 27, which is the area delineated generally by the broken lineX-X of FIGURE l, comprises two sections. The first of these is an upperand end section which comprises that portion having on its interiorsurface a plurality of prisms generally perpendicular to rim 25 of therefractor, as indicated in FIGURE 1. These prisms are shown as prisms61, 121, and 141 of FIG- URES 6, l2, and 14 respectively, and have theirbases, or their thickest portions, at their edges which are nearest to acentral bullseye area, designated as 32 in FIGURE 1. Thus, light rayspassing through this section tend to be bent in the direction of thiscentral area. Since greater refractive power is required to bend in thisdirection light which falls nearer the ends of this section, the prismsincrease in pitch with increasing distance from the central area.Central area 32 corresponds to the 74 lateral angle referred to inreference to FIGURES 18 and 19. On the exterior surface of this sectionis a plurality of prisms 131 and 151, generally parallel to rim 25 andillustrated respectively in FIGURES 13 and 15. These prisms have theirmaximum thicknesses at their edgeswhich are farthest from rim'l 25 andtherefore bend light iri directions away from the rim.

The second section of side area 27, which will be referred to as thelower section, has an interior surface having a series of prismsgenerally parallel to rim 25, as shown in FIGURE 1v. The configurationsof these prisms are illustrated as prisms 81 and 101 of FIGURES 8 and10, respectively. These prisms have their thickest edges nearest rim 25and hence tend to bend light in the direction of the rim. On theexterior surface of this lower section is a series of prisms having anarrangement similar to that of prisms 121 and 141 of the interiorsurface 0f the upper and end section of area 27.V They are generallyperpendicular to rim 25 and have their thickest edges nearest a centralarea which is a continuation of area 32 of FIGURE l and tend to causelight to converge in this direction. They are illustrated as prisms 91and 111 of FIGURES 9 and l1 respectively.

Base area 29, having its interior and exterior surfaces illustrated inplan view in FIGURES 1 and 4 respectively, refracts light away from thearea directly beneath the luminaire and spreads it away from and besidethe wall on which the luminaire is mounted. On the interior surface ofbase area 29 are a plurality of prisms 71, illustrated in section inFIGURE 3', and generally parallel to the surfaces of end area 30. Prisms71 are thickest at their edges farthest from an area 30 and hencerefract light away therefrom. The refractive power of the prismsdecreases with increasing distance from base area 30. The exteriorsurface of base area 29 is divided into three sections, illustrated insection in FIGURES 7, 16 and 17 respectively. The prisms 70 of FIGURE 7,which together with that part of the interior surface opposed theretocomprise the forward section of the base area, have slightly curvedsurfaces and consequently spread out the light passing therethrough bycausing light rays to be bent in the direction of the centers of therespective prisms and subsequently to cross and diverge. The inclinationofthe surfaces of prisms 70, which are thickest at their edges farthestfrom the longitudinal axis ofthe refractor, increases with increasingdistance from the center, and hence the cumulative effect of prisms 70and 71 is to cause light emitted from this section to be spread overawide area below and in front of the luminaire. Prisms'160 and 170 ofFIGURES 16 and 17 respectively, which together with that part of theinterior surface opposed thereto comprise the base section of base area29, are oriented at angles of approximately 45 with the longitudinalaxis of the luminaire and are thickest at their edges -farthest from endarea 30. Their function is to bend outwardly from the wall and laterallyfrom the luminaire light which would otherwise fall on the wall ordirectly under the luminaire.

It will be observed that the term prism is not used herein in its strictgeometric sense, since the structures so described are not composedsolely of plane surfaces but are of necessity curved to fit the curvedsurface areas of the refractor. VIn addition, as has been pointed out,certain prisms have refracting surfaces which are curved in crosssection as well.

Side areas 27 and 28 are formed with two sections as described in orderto avoid angular configurations which would make it impossible to removethe finished refractor from a one-piece block mold. It will be apparentto those familiar with the art that, if it is desired to use a separablemold, the side areas may equally well be made with all horizontallydeecting prisms on one surface and all vertically -deecting prisms onone surface and all vertically deecting prisms on the other surface.

It will be further apparent that end area 30 may comprise a reflectingsurface such as a silvered surface rather than the illustrated totallyreilecting prisms.

In order to direct the main beam from the luminaire at 74 in ahorizontal direction from the longitudinal axis of the luminaire, thelight center of the luminaire is placed so that the vertical bulls eyes,toward which the vertical prisms of the side and end areas refractlight, and the longitudinal axis subtend angles of 74 at the lightcenter. It will be understood, however, that modifications in theprecise light distribution illustrated may be eifected Within the scopeof the invention by variation of the location of the light center withinthe luminaire.

I claim:

1. A refractor in the generalr shape of a hollow truncated triangularpyramid having an open base forming a rim, and comprising an end area onone generally quadrangular face thereof, two symmetric side areas on theremaining generally quadrangular faces thereof, and a base area on thegenerally triangular face thereof, each of said side areas comprisingtwo sets of surface prisms, the prisms of one of said sets having edgessubstantially parallel to said rim and having bases nearest a line ontheir respective side area substantially parallel to said rim and theother of said sets having edges substantially perpendicular to said rimand having base edges nearest a line on their respective side areasubstantially perpendicularv to said rim, said end area having areflecting surface, and said base area comprising four sets of surfaceprisms, the rst set comprising a series of prisms having edgessubstantially parallel to said end area of said refractor and havingbases at their edges farthest from said end area, the second setcomprising a series of parallel prisms having edges substantiallyperpendicular to said end area and having surfaces which are curved incross section, and each of said third and fourth sets comprising aseries of parallel prisms, the prisms of said third and fourth setshaving edges substantially perpendicular and forming angles ofapproximately 45 with the prisms of said iirst and second sets.

2. A refractor according to claim l in which said second set of basearea prisms have base edges farthest from a line in said base area whichis substantially perpendicular to said end area and which divides saidbase area into two substantially equal parts.

3. A refractor in the general shape of a hollow truncated triangularpyramid having an open base forming a rim, and comprising an end area onone generally quadrangular base thereof, two symmetric side areas on theremaining generally quadrangular faces thereof and a base area on thegenerally triangular face thereof, each of said side areas comprisingtwo sets of surface prisms, the prisms of one of said sets having edgesSubstantially parallel to said rim and having base edges nearest a lineon their respective side area substantially parallel to said rim and theother of said sets having edges substantially perpendicular to said rimand having base edges nearest a line on their respective side areasubstantially perpendicular to said rim, said end area having areflecting surface, and Vsaid base area comprising a forward section anda base section, said base area having on its interior surface a seriesof prisms having edges substantially parallel to said end area of saidrefractor and bases at their respective edges farthest from said endarea, said forward section having an exterior surface comprising aseries of prisms having edges substantially perpendicular to said endarea and having surfaces which are curved in cross section, and saidbase section of said base area having an exterior surface comprising twoseries of parallel prisms, the edges of prisms of each of said seriesbeing respectively perpendicular to the edges of the prisms of the otherof said series and forming angles of approximately 45 with the edges ofsaid prisms of the exterior surface of said forward section of said basearea, and having bases at their edges farthest from said end area.

4. A refractor according to claim 3 in which said end area has a smoothinterior surface and an exterior surface comprising a series of parallelinternally reecting prisms having edges generally perpendicular to saidrim.

5. A refractor according to claim 3 in which the said prisms of theexterior surface of the forward section of the base area have base edgesfarthest from a line in said base area which line is substantiallyperpendicular to said end area and divides said base area into twosubstantially equal parts.

6. A refractor according to claim 3 in which each of said side areascomprises a lower section and an upper and end section, said lowersection having an interior surface comprising a series of prisms havingedges substantially parallel to said rim and having base edges nearestsaid rim and an exterior surface comprising a series of prisms havingedges substantially perpendicular to said rim and having base edgesnearest a line substantially perpendicular to said rim and dividing saidside area into two parts, and said upper and end section having anexterior surface comprising a series of prisms having edgessubstantially parallel to said rim and having base edges farthest fromsaid rim and an interior surface comprising a series of prisms havingedges substantially perpendicular to said rim and having base edgesnearest said line dividing said side area into two parts.

References Cited in the file of this patent UNITED STATES PATENTS804,254 Mygatt Nov. 14, 1905 1,731,714 Dorey s Oct. 15, 1929 2,739,226Rex Mar. 30, 1956 2,814,723 Franck et al. Nov. 26, 1957

1. A REFRACTOR IN THE GENERAL SHAPE OF A HOLLOW TRUNCATED TRIANGULARPYRAMID HAVING AN OPEN BASE FORMING A RIM, AND COMPRISING AN END AREA ONONE GENERALLY QUADRANGULAR FACE THEREOF, TWO SYMMETRIC SIDE AREAS ON THEREMAINING GENERALLY QUADRANGULAR FACES THEREOF, AND A BASE AREA ON THEGENERALLY TRIANGULAR FACE THEREOF, EACH OF SAID SIDE AREAS COMPRISINGTWO SETS OF SURFACE PRISMS, THE PRISMS OF ONE OF SAID SETS HAVING EDGESSUBSTANTIALLY PARALLEL TO SAID RIM AND HAVING BASES NEAREST A LINE ONTHEIR RESPECTIVE SIDE AREA SUBSTANTIALLY PARALLEL TO SAID RIM AND THEOTHER OF SAID SETS HAVING EDGES SUBSTANTIALLY PERPENDICULAR TO SAID RIMAND HAVING BASE EDGES NEAREST A LINE ON THEIR RESPECTIVE SIDE AREASUBSTANTIALLY PERPENDICULAR TO SAID RIM, SAID END AREA HAVING AREFLECTING SURFACE, AND SAID BASE AREA COMPRISING FOUR SETS OF SURFACEPRISMS, THE FIRST SET COMPRISING A SERIES OF PRISMS HAVING EDGESSUBSTANTIALLY PARALLEL TO SAID END AREA OF SAID REFRACTOR AND HAVINGBASES AT THEIR EDGES FARTHEST FROM SAID END AREA, THE SECOND SETCOMPRISING A SERIES OF PARALLEL PRISMS HAVING EDGES SUBSTANTIALLYPERPENDICULAR TO SAID END AREA AND HAVING SURFACES WHICH ARE CURVED INCROSS SECTION, AND EACH OF SAID THIRD AND FOURTH SETS COMPRISING ASERIES OF PARALLEL PRISMS, THE PRISMS OF SAID THIRD AND FOURTH SETSHAVING EDGES SUBSTANTIALLY PERPENDICULAR AND FORMING ANGLES OFAPPROXIMATELY 45* WITH THE PRISMS OF SAID FIRST AND SECOND SETS.